Question

For a movie scene, a 75-kg stuntman drops from a tree onto a 50-kg sled that is moving on a frozen lake with a velocity of 10 m/s toward the shore. (a) what is the speed of the sled after the stuntman is on board?

Answer 1

Given: 
 m1 = 75 kg
 u1 = 0.0 m/s 
 m2 = 50 kg
 u1 = 10 m/s
 Conservation of momentum, velocity of combined system from individual objects 
 v * [m1+m2] = m1u1 + m2u2 
 v * [ (75 kg) + (50 kg) ] = [ (75 kg) * (0.0 m/s) ] + [ (50 kg) * (10 m/s) ] 
 v * [ 125 kg ] = [ 500 kg-m/s ] 
 v = [ 500 kg-m/s ] / [ 125 kg ] 
 v = 4 m/s
 the speed of the sled after the stuntman is on board is 4 m/s